In the manufacture of semi-conductor wafers, metals are deposited onto the face of the wafers, typically over a barrier or seed layer of metal, to form an electronic circuitry on the workpiece. Recent interest in the use of copper as a preferred metal for use in the formation of semiconductor circuitry is motivated, at least in part, by a desire to provide conductive circuitry with lowered electrical resistance, less heat generation and a finished semi-conductor chip with increased capacity and efficiency. While chemical vapor deposition and electroplating techniques have been used to fill the via holes and trenches within silicon-based substrates, these processes generally have been very expensive and have experienced high defect densities.
The task of providing an electronic circuitry for the semi-conductor workpiece surface has required separate process steps for first depositing the metal and subsequently polishing it. Such multi-step methods have been performed on systems for electrolytic deposition having an anode and a cathode with electrolytic solutions serving as the source of metal ions. Such multi-step techniques have required first that the conductive material be deposited directly onto the surface of the workpiece. Thereafter, a separate polishing step is required, typically involving a chemical-mechanical polishing process utilizing an abrasive slurry and a conventional polishing pad to polish the surface of the wafer to the degree needed. The deposition step and the polishing step have generally been performed at separate stations in the semiconductor manufacturing line.
Recently, electro-chemical mechanical deposition (“ECMD”) methods and equipment have been described in the art. See, for example, U.S. Pat. No. 6,176,992 which describes the electrolytic deposition of a conductive material within the vias on the surface of a semi-conductor wafer while avoiding the deposition of the same conductive material at locations on the surface of the wafer outside of the vias. The conductive material is electrolytically deposited onto the workpiece surface. A slurry-free abrasive process is described to polish the conductive material after the metal has initially been deposited. Alternatively, the abrasive article may be used in a process that simultaneously deposits and polishes conductive material on the exposed surface of the semiconductor wafer. The disclosed apparatus includes an anode associated with an abrasive article and capable of receiving a first potential upon application of power. The abrasive article or pad is positioned between the anode and the wafer. The exposed surface of the wafer is conductive and receives a negative electric potential to thereby operate as the cathode to receive a second potential opposite the first potential upon application of power and to facilitate the deposition of conductive material (e.g., copper or other metal) onto the wafer surface from a suitable electrolyte solution. The abrasive article is moveable with respect of the exposed surface of the wafer to polish the wafer surface and thereby avoid the need for a separate polishing step using an abrasive slurry.
Although a significant advance in the art, the aforementioned deposition and polishing of an electrolyte on the semi-conductor wafer surface has not been free of technical issues. The delivery of electrolyte solution to the surface of the wafer and the simultaneous or near simultaneous polishing of the conductive material formed from the electrolyte has resulted in the need for abrasive articles of a well defined configuration. Such an abrasive article will be constructed to allow the delivery of the electrolyte solution and plating current through the fixed abrasive and directly onto the wafer surface. While this construction permits the selective delivery of the electrolyte and the electrical plating current to the desired areas of the wafer, the application of plating current during the deposition process has occasionally caused plating of conductive material onto the working surface of the abrasive article. The presence of plated metal on the working surface of the abrasive article can scratch the working surface of the wafer as well as shorten the working life of the abrasive article.
For at least the foregoing reasons, there is a need for an abrasive article for use in ECMD wherein the article is constructed to permit the flow of electrolyte therethrough while minimizing the aforementioned problem of metal plating on the working surface of the abrasive.